What is Mitosis?

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What is Mitosis?
Mitosis is when the cells nucleus divides into
two new nuclei and one copy of the DNA is
distributed into each daughter cell. New cells
formed are called daughter cells.
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Why Do Cells Need to Divide?
Cells want to divide for several reasons 1)
Large cells cant control their functions as well
as small cells-- as a cell gets bigger, it still
the same amount of DNA to do the same jobs 2)
Large cells cant exchange materials as well--
the ratio of surface area (cell membrane) to cell
volume decreases as a cell gets bigger, making it
harder for food to get in and wastes to go out 3)
As cells age, they arent as efficient
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The Cell Cycle
Cells arent constantly dividing instead, cells
grow, live their lives and then divide when
necessary. Cell cycle -- this process of growth
and division is known as the The cell cycle
consists of three parts Interphase --
interphase is further divided into three parts
Mitosis -- mitosis is also divided into four
parts called prophase, metaphase, anaphase,
and telophase Cytokinesis -- Completes the
process of cell division
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Image of the Cell Cycle
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Interphase
The cell cycle begins when a new daughter cell is
formed and immediately begins interphase. During
interphase, the cell undergoes the following life
phases 1. Cells grow to their mature size 2.
Cells replicate their DNA so that they have a
copy for each new daughter cell. 3. Cells also
manufacture new proteins and organelles preparing
to divide into two cells. ONCE THIS HAPPENS
MITOSIS IS READY TO BEGIN!!
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About Chromosomes
Chromosomes are only visible when mitosis is
about to begin and during mitosis. Chromosomes
consist of a chromatid (a strand of DNA) with a
condensed area called the centromere.
Centromeres are near the middle of a
chromatid. DNA (and therefore chromosomes) are
replicated during the interphase, so each
chromosome actually consists of two sister
chromatids. Humans have 23 matching pairs of
chromosomes, for a grand total of 46 chromosomes
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Image of a Chromosome
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Mitosis
Biologists usually consider the first four parts
to be actual mitosis, The parts of mitosis
are -- prophase -- metaphase -- anaphase --
telophase The final part of the cell cycle,
cytokinesis, happens later.
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Prophase
Prophase is the longest phase of mitosis During
prophase -- the centrioles line up on opposite
sides of the nucleus
1. Chromatin condenses into visible
chromosomes 2. Structures called spindle fibers
form a bridge between each end of the cell. 3.
Nucleolus disappears and nuclear membrane breaks
down
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Metaphase
Metaphase only last for a few minutes During
metaphase 1. Chromosomes line up across the
center of the cell 2. Chromosome attach to the
spindle fibers at the centromere
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Anaphase
During anaphase 1. Centromeres that join sister
chromatids separate and the chromatids become
individual chromosomes 2. Chromosomes move apart
until they reach the centrioles near the end of
the spindle 3. Cell becomes stretched out as the
opposite ends pull apart.
Anaphase ends when the centrioles stop moving
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Telophase
During telophase 1. Chromosomes begin to tangle
back into chromatin and lose their rod-like
appearance 2. Nuclear membrane begins to re-form
around each set of chromosomes 3. Spindle fibers
break 4. Nuceloli become visible in each new
nucleus
END OF MITOSIS
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Cytokinesis
Although cells have split up their genetic
material and formed new nuclei, the cells are not
split. Cytokinesis is the process by which cells
split their cytoplasm into two new daughter
cells In animals, cytokinesis happens when the
cell membrane is drawn in and the cell divides
into two new cells In plants, a structure made of
wall-building vesicles, called a cell plate forms
between the two new nuclei, and eventually
becomes a dividing membrane
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Full Diagram of Mitosis